In recent years, development of technology for wirelessly transmitting power (electric energy) without using power cords and the like has been popular. Among the methods of wirelessly transmitting power, a so-called magnetic resonance method is the technology that has been attracting particular attention. The magnetic resonance method was proposed by a research group at the Massachusetts Institute of Technology in 2007. The relevant technique has been disclosed in Patent Document 1 (Jpn. PCT National Publication No. 2009-501510), for example.
In a wireless power transmission system of the magnetic resonance method, the resonance frequency of a power transmission-side antenna is equal to the resonance frequency of a power reception-side antenna. Accordingly, the energy is transmitted from the power transmission-side antenna to the power reception-side antenna in an efficient manner. One of the major features is the power transmission distance that can be set to between several tens of centimeters and several meters.
If the above-described wireless power transmission system of the magnetic resonance method is used in a power supply station for such vehicles as electric cars, a power reception-side antenna may be mounted in a bottom portion of a vehicle, and power may be supplied to the power reception-side antenna from a power transmission-side antenna that is buried in the ground. In cases where power is transmitted in that manner, it is difficult for the power transmission-side antenna to be completely and electromagnetically coupled to the power reception-side antenna. Some noise would emerge as the noise is emitted from the antennas, possibly leading to a rise in the temperature of the metal used in the bottom portion of the vehicle body and the like.
Accordingly, a study needs to be done to look into ways to reduce the noise generated from the antennas in the wireless power transmission system.
Incidentally, as a technique for reducing high-frequency noise, for example, Patent Document 2 (JP2010-87024A) discloses a resonant circuit including a conductor, which is provided near a source of noise in such a way as to have a looped closed path, and a capacitor, which is electrically connected to the closed path.
[Patent Document 1]
Jpn. PCT National Publication No. 2009-501510
[Patent Document 2]
JP2010-87024A